Communication systems having multiple transmitter sites, such as cellular telephone systems, are known in the art. In such a system, a user typically contacts another user by entering an identification code, such as a telephone number, to identify the second user. With this information, the system then establishes a communication path between the two users, and a conversation (or other mode of communication) then ensues.
Dispatch communication systems are also known. In such a system, a user will typically not enter a specific code to identify a specific user. Instead, the user's communication unit will have predetermined talk groups programmed into it to automatically provide the system with the appropriate information to allow establishment of a dispatch call. Therefore, the user often simply keys the microphone and begins talking without the need for any dialing or manual user selection mechanisms at all. The intended listener, being a member of the defined talk group (and all other members of the same talk group), will generally receive this voice communication, and the communication path establishment protocol is substantially transparent to the users.
To date, there have been no systems that combine the spectral efficiencies of geographic reuse (as typified in the cellular telephone infrastructure) with the user conveniences offered by a dispatch system. This is primarily because, while most radio dispatch communications are between two particular radio users, these users belong to a talk group having members that can be widely geographically distributed. Therefore, the potential benefits of geographic reuse vanish, as many transmitter sites (cells) must be allocated to support the communication, even though the two users occupy, at most, only two cells.
Accordingly, a need exists for a system that offers at least some of the merits of both types of system.